1. Field of the Invention
The application is in the field of pulsed laser systems, and more specifically in the field of chirped pulse amplification systems.
2. Related Art
Chirped pulse amplification (CPA) is very useful for producing ultrashort-duration high-intensity pulses for use in high peak power ultrashort pulse laser systems. CPA increases the energy of an ultrashort laser pulse while avoiding optical amplifier damage. In this technique, the duration of the pulse is increased by first dispersing the ultrashort laser pulse temporally as a function of wavelength (a process called “chirping”) to produce a chirped pulse, amplifying the chirped pulse, and then recompressing the chirped pulse to significantly shorten its duration. Lengthening the pulse in time reduces the peak power of the pulse and, thus, allows energy to be added to the pulse without reaching a damage threshold of the pulse amplifier and other optical components.
Some elements in a CPA system are polarization sensitive. For example, the performance of a pulse compressor that uses gratings to compress a laser pulse is highly polarization sensitive. Some elements in a CPA system alter polarizing in ways that are not precisely predictable. For example, passage of a pulse through a non polarization-maintaining (PM) fiber optic may alter the polarization of the pulse somewhat. This alteration can include a transformation of the polarization state into linear, circular or elliptical polarization.
The degree to which polarization is altered may be temperature or pulse power dependent, and may, therefore, be time dependent. This is a problem when subsequent elements within the CPA system are polarization sensitive, because their performance may be dependent on, for example, the temperature of polarization altering elements.
There is, therefore, a need for improved methods of managing polarization in CPA systems.